Disagreement exists among visual scientists on the relative temporal properties of human L and M cones and the effect of cone adaptation on temporal response. I will use the flicker electroretinogram (fERG) technique and psychophysical methods, to investigate temporal properties and adaptation in the Fourier frequency domain. I will use an admixture of red and green counter-phase flicker as the stimulus to change the relative responses of L and M cones, and measure the relative responses as a function of the flicker frequency and cone adaptation levels. A theoretical model has been developed to specify experimental design. Specifically, I will: (1) test the adaptation dependent hypothesis by partially adapting the L and M cones and looking at a null-position change with flicker frequency, in which the response modulations in L and M cones are equal but out of phase, consequently no electrical activity will be recorded in the fundamental components of fERG, and no flicker will be experienced. (2) test the hypothesis that L cones differ from M cones in temporal properties by changing the illuminance levels of flicker stimuli and looking at the null-position change with flicker frequency. (3) test the hypothesis that L cone differs from M cone in temporal property only with a time or phase delay by introducing phase difference between red and green flickers and analyzing the overall fERG fundamental responses. (4) measure the temporal property of L and M cones at specific adaptation levels by partially bleaching one cone type. A decisive conclusion on the relative temporal property of human L and M cones and the effect of cone adaptation will be reached after this experiment